1. Field of the Invention
The present invention relates to barrier operator systems and, more particularly, relates to a modulated DC motor for controlling the operation of a movable barrier such as a garage door or gate or door with a non-linear motion control profile.
2. Description of Related Art
Barrier operators, such as garage door and gate operators, have become more sophisticated by providing greater user convenience, improvements in operational speed, safety, ease of installation, and decreased noise output. DC motor-based garage door operators have gained user preference in comparison to AC motor based garage door operators due to their quieter operation, increased reliability, and smoother movements.
Along with improved reliability, DC motor-based garage door operators provide an increased operational life, which can be attributed to the reduced stress on the garage door transmission system. DC motor-based garage door operators provide a less abrupt, jarring motion during start and stop movements as compared with AC motor-based garage door operators.
Some DC motor-based operators of the prior art attempt to improve motor control by use of a linear speed ramp for opening and closing motions. Prior art operators, for example, may use a linear motion profile based on predetermined speed values. While this is an improvement over full speed start-and stop-type profiles, the profiles of such operators are still not optimal.
Other prior art garage door operators use a DC motor that is pulse width modulated directly off the AC main. The motion control strategy employed by such operators is traditional constant speed on/off control. The motor speed is fixed based on door travel distance.